Dual nozzle single horizontal fulcrum actuator ink jet printing mechanism

ABSTRACT

An ink jet printing apparatus for ejecting fluids from a nozzle chamber has at least two fluid ejection apertures defined in the walls of the chamber; a moveable paddle vane located in a plane adjacent the rim of a first one of the fluid ejection apertures; and an actuator mechanism attached to the moveable paddle vane and adapted to move the paddle vane in a first direction so as to cause the ejection of fluid drops out of the first fluid ejection aperture and to further move the paddle vane in a second alternative direction so as to cause the ejection of fluid drops out of a second fluid ejection aperture. The apparatus can include a baffle located between the first and second fluid ejection apertures such that the paddle vane moving in the first direction causes an increase in pressure of the fluid in the volume adjacent the first aperture and a simultaneous decrease in pressure of the fluid in the volume adjacent the second aperture. Further, the paddle vane moving in the second direction can cause an increase in pressure of the fluid in the volume adjacent the second aperture and a simultaneous decrease in pressure of the fluid in the volume adjacent the first aperture.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application Ser. Nos. (USSN) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.

CROSS- US PATENT APPLICATION REFERENCED (CLAIMING RIGHT AUSTRALIAN OF PRIORITY PROVISIONAL FROM AUSTRALIAN DOCKET PATENT NO. PROVISIONAL APPLICATION) NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO9399 09/112,791 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065 09/113,111 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 09/113,089 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19 PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO8006 09/113,100 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010 09/113,064 MEMS05 PO8011 09/113,082 MEMS06 PO7947 09/113,081 MEMS07 PO7944 09/113,080 MEMS09 PO7946 09/113,079 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The field of the invention relates to the field of inkjet printing and in particular, discloses an inkjet printing arrangement including a dual nozzle single horizontal fulcrum actuator inkjet printer.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number of which are presently in use. The known forms of printing have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles, has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques which rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.

With any inkjet printing arrangement, particularly those formed in a page wide inkjet printhead, it is desirable to minimise the dimensions of the arrangement so as to ensure compact economical construction. Further, it is desirable to provide for energy efficient operation.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for an alternative from of inkjet printhead including a multi-nozzled arrangement wherein a single actuator is used to eject ink from multiple nozzles.

In accordance with a first aspect of the present invention, there is provided an apparatus for ejecting fluids from a nozzle chamber including a nozzle chamber having at least two fluid ejection apertures defined in the walls of the chamber; a moveable paddle vane located in a plane adjacent the rim of a first one of the fluid ejection apertures; and an actuator mechanism attached to the moveable paddle vane and adapted to move the paddle vane in a first direction so as to cause the ejection of fluid drops out of the first fluid ejection aperture and to further move the paddle vane in a second alternative direction so as to cause the ejection of fluid drops out of a second fluid ejection aperture.

The apparatus can include a baffle located between the first and second fluid ejection apertures such that the paddle vane moving in the first direction causes an increase in pressure of the fluid in the volume adjacent the first aperture and a simultaneous decrease in pressure of the fluid in the volume adjacent the second aperture. Further, the paddle vane moving in the second direction can cause an increase in pressure of the fluid in the volume adjacent the second aperture and a simultaneous decrease in pressure of the fluid in the volume adjacent the first aperture.

The paddle vane and the actuator can be interconnected so as to pivot around a wall of the chamber and the apparatus can further comprise a fluid supply channel connecting the nozzle chamber with a fluid supply for supplying fluid to the nozzle chamber, the connection being in a wall of the chamber substantially adjacent the pivot point of the paddle vane.

One wall of the nozzle chamber can include at least one smaller aperture interconnecting the nozzle chamber with an ambient atmosphere, the size of the smaller aperture being of such dimensions that, during normal operation of the apparatus, the net flow of fluid through the smaller aperture is zero.

The actuator can comprise a thermal actuator having at least two heater elements with a first of the elements being actuated to cause the paddle vane to move in a first direction and a second heater element being actuated to cause the paddle vane to move in a second direction. The heater elements preferably have a high bend efficiency wherein the bend efficiency is defined as the youngs modulus times the coefficient of thermal expansion divided by the density and by the specific heat capacity.

The heater elements can be arranged on opposite sides of a central arm, the central arm having a low thermal conductivity. The central arm can comprise substantially glass. The paddle vane and the actuator are preferably joined at a fulcrum pivot point, the fulcrum pivot point comprising a thinned portion of the nozzle chamber wall. The thermal actuator preferably operates in an ambient atmosphere and the thinned portion of the nozzle chamber wall can include a series of slots at opposing sides so as to allow for the flexing of the wall during actuation of the actuator. Preferably, the external surface adjacent the slots comprises a planar or concave surface so as to reduce wicking. The fluid ejection apertures can include a rim defined around an outer surface thereof.

Further, the thermal actuator can include one end attached to a substrate and a second end having a thinned portion, the thinned portion providing for the flexible attachment of the actuator to the moveable paddle vane.

A large number of fluid ejection apertures can be grouped together spatially into spaced apart rows and fluid ejected from the fluid ejection apertures of each of the rows in phases. The apparatuses can be ideally utilized for ink jet printing with the nozzle chambers further being grouped into multiple ink colors and with each of the nozzles being supplied with a corresponding ink color.

In accordance with a second aspect of the present invention, there is provided a method of ejecting drops of fluid from a nozzle chamber having at least two nozzle apertures defined in the wall of the nozzle chambers utilizing a moveable paddle vane attached to an actuator mechanism, the method comprising the steps of: actuating the actuator to cause the moveable paddle to move in a first direction so as to eject drops from a first of the nozzle apertures; and actuating the actuator to cause the moveable paddle to move in a second direction so as to eject drops from a second of the nozzle apertures.

An array of nozzle chambers can be arranged in a pagewidth print head and the moveable paddles of each nozzle chamber are driven in phase for the ejection of ink onto a page.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIGS. 1-5 illustrate schematically the principles operation of the preferred embodiment;

FIG. 6 is a perspective view, partly in section of one form of construction of the preferred embodiment;

FIGS. 7-24 illustrate various steps in the construction of the preferred embodiment; and

FIG. 25 illustrates an array view illustrating a portion of a printhead constructed in accordance with the preferred embodiment.

FIG. 26 provides a legend of the materials indicated in FIGS. 27 to 42; and

FIG. 27 to FIG. 43 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, an inkjet printing system is provided for the projection of ink from a series of nozzles. In the preferred embodiment a single paddle is located within a nozzle chamber and attached to an actuator device. When the nozzle is actuated in a first direction, ink is ejected through a first nozzle aperture and when the actuator is activated in a second direction causing the paddle to move in a second direction, ink is ejected out of a second nozzle. Turning initially to FIGS. 1-5, there will now be illustrated in a schematic form, the operational principles of the preferred embodiment.

Turning initially to FIG. 1, there is shown a nozzle arrangement 1 of the preferred embodiment when in its quiescent state. In the quiescent state, ink fills a first portion 2 of the nozzle chamber and a second portion 3 of the nozzle chamber. A baffle is situated between the first portion 2 and the second portion 3 of the nozzle chamber. The ink fills the nozzle chambers from an ink supply channel 5 to the point that a meniscus 6, 7 is formed around corresponding nozzle holes 8, 9. A paddle 10 is provided within the nozzle chamber 2 with the paddle 10 being interconnected to a actuator device 12 which can comprise a thermal actuator which can be actuated so as to cause the actuator 12 to bend, as will be become more apparent hereinafter.

In order to eject ink from the first nozzle hole 9, the actuator 12, which can comprise a thermal actuator, is activated so as to bend as illustrated in FIG. 2. The bending of actuator 12 causes the paddle 10 to rapidly move upwards which causes a substantial increase in the pressure of the fluid, such as ink, within nozzle chamber 2 and adjacent to the meniscus 7. This results in a general rapid expansion of the meniscus 7 as ink flows through the nozzle hole 9 with result of the increasing pressure. The rapid movement of paddle 10 causes a reduction in pressure along the back surface of the paddle 10. This results in general flows as indicated 17, 18 from the second nozzle chamber and the ink supply channel. Next, while the meniscus 7 is extended, the actuator 12 is deactivated resulting in the return of the paddle 10 to its quiescent position as indicated in FIG. 3. The return of the paddle 10 operates against the forward momentum of the ink adjacent the meniscus 7 which subsequently results in the breaking off of the meniscus 7 so as to form the drop 20 as illustrated in FIG. 3. The drop 20 continues onto the print media. Further, surface tension effects on the ink meniscus 7 and ink meniscus 6 result in ink flows 21-23 which replenish the nozzle chambers. Eventually, the paddle 10 returns to its quiescent position and the situation is again as illustrated in FIG. 1.

Subsequently, when it is desired to eject a drop via ink ejection hole 8, the actuator 12 is activated as illustrated in FIG. 14. The actuation 12 causes the paddle 10 to move rapidly down causing a substantial increase in pressure in the nozzle chamber 3 which results in a rapid growth of the meniscus 6 around the nozzle hole 8. This rapid growth is accompanied by a general collapse in meniscus 7 as the ink is sucked back into the chamber 2. Further, ink flow also occurs into ink supply channel 5 however, hopefully this ink flow is minimised. Subsequently, as indicated in FIG. 5, the actuator 12 is deactivated resulting in the return of the paddle 10 to is quiescent position. The return of the paddle 10 results in a general lessening of pressure within the nozzle chamber 3 as ink is sucked back into the area under the paddle 10. The forward momentum of the ink surrounding the meniscus 6 and the backward momentum of the other ink within nozzle chamber 3 is resolved through the breaking off of an ink drop 25 which proceeds towards the print media. Subsequently, the surface tension on the meniscus 6 and 7 results in a general ink inflow from nozzle chamber 5 resulting, in the arrangement returning to the quiescent state as indicated in FIG. 1.

It can therefore be seen that the schematic illustration of FIG. 1 to FIG. 5 describes a system where a single planar paddle is actuated so as to eject ink from multiple nozzles.

Turning now to FIG. 6, there is illustrated a sectional view through one form of implementation of a single nozzle arrangement 1. The nozzle arrangement 1 can be constructed on a silicon wafer base 28 through the construction of large arrays of nozzles at one time using standard micro electromechanical processing techniques.

An array of nozzles on a silicon wafer device and can be constructed using semiconductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed.

For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.

One form of construction will now be described with reference to FIGS. 7 to 24. On top of the silicon wafer 28 is first constructed a CMOS processing layer 29 which can provide for the necessary interface circuitry for driving the thermal actuator and its interconnection with the outside world. The CMOS layer 29 being suitably passivated so as to protect it from subsequent MEMS processing techniques. The walls eg. 30 can be formed from glass (SiO₂). Preferably, the paddle 10 includes a thinned portion 32 for more efficient operation. Additionally, a sacrificial etchant hole 33 is provided for allowing more effective etching of sacrificial etchants within the nozzle chamber 2. The ink supply channel 5 is generally provided for interconnecting an ink supply conduit 34 which can be etched through the wafer 28 by means of a deep anisotropic trench etcher such as that available from Silicon Technology Systems of the United Kingdom.

The arrangement 1 further includes a thermal actuator device eg. 12 which includes two arms comprising an upper arm 36 and a lower arm 37 extending from a port 55 and formed around a glass core 38. Both upper and lower arm heaters 36, 37 can comprise a 0.4μ film of 60% copper and 40% nickel hereinafter known as (Cupronickel) alloy. Copper and nickel is used because it has a high bend efficiency and is also highly compatible with standard VLSI and MEMS processing techniques. The bend efficiency can be calculated as the square of the coefficient of the thermal expansion times the Young's modulus, divided by the density and divided by the heat capacity. This provides a measure of the amount of “bend energy” produced by a material per unit of thermal (and therefore electrical) energy supplied.

The core can be fabricated from glass which also has many suitable properties in acting as part of the thermal actuator. The actuator 12 includes a thinned portion 40 for providing an interconnect between the actuator and the paddle 10. The thinned portion 40 provides for non-destructive flexing of the actuator 12. Hence, when it is desired to actuate the actuator 12, say to cause it to bend downwards, a current is passed down through the top cupronickel layer causing it to be heated and expand. This in turn causes a general bending due to the thermocouple relationship between the layers 36 and 38. The bending down of the actuator 36 also causes thinned portion 40 to move downwards in addition to the portion 41. Hence, the paddle 10 is pivoted around the wall 41 which can, if necessary, include slots for providing for efficient bending. Similarly, the heater coil 37 can be operated so as to cause the actuator 12 to bend up with the consequential movement upon the paddle 10.

A pit 39 is provided adjacent to the wall of the nozzle chamber to ensure that any ink outside of the nozzle chamber has minimal opportunity to “wick” along the surface of the printhead as, the wall 41 can be provided with a series of slots to assist in the flexing of the fulcrum.

Turning now to FIGS. 7-24, there will now be described one form of processing construction of the preferred embodiment of FIG. 6. This can involve the following steps:

1. Initially, as illustrated in FIG. 7, starting with a fully processed CMOS wafer 28 the CMOS layer 29 is deep silicon etched so as to provide for the nozzle ink inlet 5.

2. Next, as illustrated in FIG. 8, a 7μ layer 42 of a suitable sacrificial material (for example, aluminium), is deposited and etched with a nozzle wall mask in addition to the electrical interconnect mask.

3. Next, as illustrated in FIG. 9, a 7μ layer of low stress glass 42 is deposited and planarised using chemical planarization.

4. Next, as illustrated in FIG. 10, the sacrificial material is etched to a depth of 0.4 micron and the glass to at least a level of 0.4 micron utilising a first heater mask.

5. Next, as illustrated in FIG. 11, the glass layer is etched 45, 46 down to the aluminium portions of the CMOS layer 4 providing for an electrical interconnect using a first heater via mask.

6. Next, as illustrated in FIG. 12, a 3 micron layer 48 of 50% copper and 40% nickel alloy is deposited and planarised using chemical mechanical planarization.

7. Next, as illustrated in FIG. 13, a 4 micron layer 49 of low stress glass is deposited and etched to a depth of 0.5 micron utilising a mask for the second heater.

8. Next, as illustrated in FIG. 14, the deposited glass layer is etched 50 down to the cupronickel using a second heater via mask.

9. Next, as illustrated in FIG. 15, a 3 micron layer 51 of cupronickel is deposited 51 and planarised using chemical mechanical planarization.

10. As illustrated in FIG. 16, next, a 7 micron layer 52 of low stress glass is deposited.

11. The glass 52 is etched, as illustrated in FIG. 17 to a depth of 1 micron utilising a first paddle mask.

12. Next, as illustrated in FIG. 18, the glass 52 is again etched to a depth of 3 micron utilising a second paddle mask with the first mask utilised in FIG. 17 etching away those areas not having any portion of the paddle and the second mask as illustrated in FIG. 18 etching away those areas having a thinned portion. Both the first and second mask of FIG. 17 and FIG. 18 can be a timed etch.

13. Next, as illustrated in FIG. 19, the glass 52 is etched to a depth of 7 micron using a third paddle mask. The third paddle mask leaving the nozzle wall 30, baffle 11, thinned wall 41 and end portion 54 which fixes one end of the thermal actuator firmly to the substrate.

14. The next step, as illustrated in FIG. 20, is to deposit an 11 micron layer 55 of sacrificial material such as aluminium and planarize the layer utilising chemical mechanical planarization.

15. As illustrated in FIG. 21, a 3 micron layer 56 of glass is deposited and etched to a depth of 1 micron utilising a nozzle rim mask.

16. Next, as illustrated in FIG. 22, the glass 56 is etched down to the sacrificial layer using a nozzle mask so as to form the nozzle structure 58.

17. The next step, as illustrated in FIG. 23, is to back etch an ink supply channel 34 using a deep silicon trench etcher such as that available from Silicon Technology Systems. The printheads can also be diced by this etch.

18. Next, as illustrated in FIG. 24, the sacrificial layers are etched away by means of a wet etch and wash.

The printheads can then be inserted in an ink chamber moulding, tab bonded and a PTFE hydrophobic layer evaporated over the surface so as to provide for a hydrophobic surface.

In FIG. 25, there is illustrated a portion of a page with printhead including a series of nozzle arrangements as constructed in accordance with the principles of the preferred embodiment. The array 60 has been constructed for three color output having a first row 61 a second row 62 and a third row 63. Additionally, a series of bond pads, eg. 64, 65 are provided at the side for tab automated bonding to the printhead. Each row 61, 62, 63 can be provided with a different color ink including cyan, magenta and yellow for providing full color output. The nozzles of each row 61-63 are further divided into sub rows eg. 68, 69. Further, a glass strip 70 can be provided for anchoring the actuators of the row 63 in addition to providing for alignment for the bond pad 64, 65.

The CMOS circuitry can be provided so as to fire the nozzles with the correct timing relationships. For example, each nozzle in the row 68 is fired together followed by each nozzle in the row 69 such that a single line is printed.

It could be therefore seen that the preferred embodiment provides for an extremely compact arrangement of an inkjet printhead which can be made in a highly inexpensive manner in large numbers on a single silicon wafer with large numbers of printheads being made simultaneously. Further, the actuation mechanism provides for simplified complexity in that the number of actuators is halved with the arrangement of the preferred embodiment.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. Relevant features of the wafer at this step are shown in FIG. 27. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 26 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.

2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the ink inlet hole.

3. Etch silicon to a depth of 15 microns using etched oxide as a mask. The sidewall slope of this etch is not critical (75 to 90 degrees is acceptable), so standard trench etchers can be used. This step is shown in FIG. 28.

4. Deposit 7 microns of sacrificial aluminum.

5. Etch the sacrificial layer using Mask 2, which defines the nozzle walls and actuator anchor. This step is shown in FIG. 29.

6. Deposit 7 microns of low stress glass and planarize down to aluminum using CMP.

7. Etch the sacrificial material to a depth of 0.4 microns, and glass to a depth of at least 0.4 microns, using Mask 3. This mask defined the lower heater. This step is shown in FIG. 30.

8. Etch the glass layer down to aluminum using Mask 4, defining heater vias. This step is shown in FIG. 31.

9. Deposit 1 micron of heater material (e.g. titanium nitride (TiN)) and planarize down to the sacrificial aluminum using CMP. This step is shown in FIG. 32.

10. Deposit 4 microns of low stress glass, and etch to a depth of 0.4 microns using Mask 5. This mask defines the upper heater. This step is shown in FIG. 33.

11. Etch glass down to TiN using Mask 6. This mask defines the upper heater vias.

12. Deposit 1 micron of TiN and planarize down to the glass using CMP. This step is shown in FIG. 34.

13. Deposit 7 microns of low stress glass.

14. Etch glass to a depth of 1 micron using Mask 7. This mask defines the nozzle walls, nozzle chamber baffle, the paddle, the flexure, the actuator arm, and the actuator anchor. This step is shown in FIG. 35.

15. Etch glass to a depth of 3 microns using Mask 8. This mask defines the nozzle walls, nozzle chamber baffle, the actuator arm, and the actuator anchor. This step is shown in FIG. 36.

16. Etch glass to a depth of 7 microns using Mask 9. This mask defines the nozzle walls and the actuator anchor. This step is shown in FIG. 37.

17. Deposit 11 microns of sacrificial aluminum and planarize down to glass using CMP. This step is shown in FIG. 38.

18. Deposit 3 microns of PECVD glass.

19. Etch glass to a depth of 1 micron using Mask 10, which defines the nozzle rims. This step is shown in FIG. 39.

20. Etch glass down to the sacrificial layer (3 microns) using Mask 11, defining the nozzles and the nozzle chamber roof. This step is shown in FIG. 40.

21. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

22. Back-etch the silicon wafer to within approximately 10 microns of the front surface using Mask 12. This mask defines the ink inlets which are etched through the wafer. The wafer is also diced by this etch. This etch can be achieved with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems. This step is shown in FIG. 41.

23. Etch all of the sacrificial aluminum. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 42.

24. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.

25. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

26. Hydrophobize the front surface of the printheads.

27. Fill the completed printheads with ink and test them. A filled nozzle is shown in FIG. 43. It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.

Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications.

The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.

For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of ink jet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 above which matches the docket numbers in the table under the heading Cross References to Related Applications.

Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently availableink jet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a print technology may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Thermal An electrothermal Large force High power Canon Bubblejet bubble heater heats the ink to generated Ink carrier limited 1979 Endo et al GB above boiling point, Simple to water patent 2,007,162 transferring significant construction Low efficiency Xerox heater-in- heat to the aqueous No moving parts High temperatures pit 1990 Hawkins et ink. A bubble Fast operation required al U.S. Pat. No. 4,899,181 nucleates and quickly Small chip area High mechanical Hewlett-Packard forms, expelling the required for actuator stress TIJ 1982 Vaught et ink. Unusual materials al U.S. Pat No. 4,490,728 The efficiency of the required process is low, with Large drive typically less than transistors 0.05% of the electrical Cavitation causes energy being actuator failure transformed into Kogation reduces kinetic energy of the bubble formation drop. Large print heads are difficult to fabricate Piezo- A piezoelectric crystal Low power Very large area Kyser et al U.S. Pat. No. electric such as lead lanthanum consumption required for actuator 3,946,398 zirconate (PZT) is Many ink types Difficult to Zoltan U.S. Pat. No. electrically activated, can be used integrate with 3,683,212 and either expands, Fast operation electronics 1973 Stemme shears, or bends to High efficiency High voltage U.S. Pat. No. 3,747,120 apply pressure to the drive transistors Epson Stylus ink, ejecting drops. required Tektronix Full pagewidth IJ04 print heads impractical due to actuator size Requires electrical poling in high field strengths during manufacture Electro- An electric field is Low power Low maximum Seiko Epson, Usui strictive used to activate consumption strain (approx. et all JP 253401/96 electrostriction in Many ink types 0.01%) IJ04 relaxor materials such can be used Large area as lead lanthanum Low thermal required for actuator zirconate titanate expansion due to low strain (PLZT) or lead Electric field Response speed is magnesium niobate strength required marginal (˜10 μs) (PMN). (approx. 3.5 V/μm) High voltage can be generated drive transistors without difficulty required Does not require Full pagewidth electrical poling print heads impractical due to actuator size Ferro- An electric field is Low power Difficult to IJ04 electric used to induce a phase consumption integrate with transition between the Many ink types electronics antiferroelectric (AFE) can be used Unusual materials and ferroelectric (FE) Fast operation such as PLZSnT are phase. Perovskite (<1 μs) required materials such as tin Relatively high Actuators require modified lead longitudinal strain a large area lanthanum zirconate High efficiency titanate (PLZSnT) Electric field exhibit large strains of strength of around 3 up to 1% associated V/μm can be readily with the AFE to FE provided phase transition. Electro- Conductive plates are Low power Difficult to IJ02, IJ04 static plates separated by a consumption operate electrostatic compressible or fluid Many ink types devices in an dielectric (usually air). can be used aqueous Upon application of a Fast operation environment voltage, the plates The electrostatic attract each other and actuator will displace ink, causing normally need to be drop ejection. The separated from the conductive plates may ink be in a comb or Very large area honeycomb structure, required to achieve or stacked to increase high forces the surface area and High voltage therefore the force. drive transistors may be required Full pagewidth print heads are not competitive due to actuator size Electro- A strong electric field Low current High voltage 1989 Saito et al, static pull is applied to the ink, consumption required U.S. Pat. No. 4,799,068 on ink whereupon Low temperature May be damaged 1989 Miura et al, electrostatic attraction by sparks due to air U.S. Pat. No. 4,810,954 accelerates the ink breakdown Tone-jet towards the print Required field medium. strength increases as the drop size decreases High voltage drive transistors required Electrostatic field attracts dust Permanent An electromagnet Low power Complex IJ07, IJ10 magnet directly attracts a consumption fabrication electro- permanent magnet, Many ink types Permanent magnetic displacing ink and can be used magnetic material causing drop ejection. Fast operation such as Neodymium Rare earth magnets High efficiency Iron Boron (NdFeB) with a field strength Easy extension required. around 1 Tesla can be from single nozzles High local used. Examples are: to pagewidth print currents required Samarium Cobalt heads Copper (SaCo) and magnetic metalization should materials in the be used for long neodymium iron boron electromigration family (NdFeB, lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usually infeasible Operating temperature limited to the Curie temperature (around 540 K) Soft A solenoid induced a Low power Complex IJ01, IJ05, IJ08, magnetic magnetic field in a soft consumption fabrication IJ10, IJ12, IJ14, core electro- magnetic core or yoke Many ink types Materials not IJ15, IJ17 magnetic fabricated from a can be used usually present in a ferrous material such Fast operation CMOS fab such as as electroplated iron High efficiency NiFe, CoNiFe, or alloys such as CoNiFe Easy extension CoFe are required [1], CoFe, or NiFe from single nozzles High local alloys. Typically, the to pagewidth print currents required soft magnetic material heads Copper is in two parts, which metalization should are normally held apart be used for long by a spring. When the electromigration solenoid is actuated, lifetime and low the two parts attract, resistivity displacing the ink. Electroplating is required High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force acts as a IJ06, IJ11, IJ13, force acting on a current consumption twisting motion IJ16 carrying wire in a Many ink types Typically, only a magnetic field is can be used quarter of the utilized. Fast operation solenoid length This allows the High efficiency provides force in a magnetic field to be Easy extension useful direction supplied externally to from single nozzles High local the print head, for to pagewidth print currents required example with rare heads Copper earth permanent metalization should magnets. be used for long Only the current electromigration carrying wire need be lifetime and low fabricated on the print- resistivity head, simplifying Pigmented inks materials are usually requirements. infeasible Magneto- The actuator uses the Many ink types Force acts as a Fischenbeck, U.S. Pat. No. striction giant magnetostrictive can be used twisting motion 4,032,929 effect of materials Fast operation Unusual materials IJ25 such as Terfenol-D (an Easy extension such as Terfenol-D alloy of terbium, from single nozzles are required dysprosium and iron to pagewidth print High local developed at the Naval heads currents required Ordnance Laboratory, High force is Copper hence Ter-Fe-NOL). available metalization should For best efficiency, the be used for long actuator should be pre- electromigration stressed to approx. 8 lifetime and low MPa. resistivity Pre-stressing may be required Surface Ink under positive Low power Requires Silverbrook, EP tension pressure is held in a consumption supplementary force 0771 658 A2 and reduction nozzle by surface Simple to effect drop related patent tension. The surface construction separation applications tension of the ink is No unusual Requires special reduced below the materials required in ink surfactants bubble threshold, fabrication Speed may be causing the ink to High efficiency limited by surfactant egress from the nozzle. Easy extension properties from single nozzles to pagewidth print heads Viscosity The ink viscosity is Simple Requires Silverbrook, EP reduction locally reduced to construction supplementary force 0771 658 A2 and select which drops are No unusual to effect drop related patent to be ejected. A materials required in separation applications viscosity reduction can fabrication Requires special be achieved Easy extension ink viscosity electrothermally with from single nozzles properties most inks, but special to pagewidth print High speed is inks can be engineered heads difficult to achieve for a 100:1 viscosity Requires reduction. oscillating ink pressure A high temperature difference (typically 80 degrees) is required Acoustic An acoustic wave is Can operate Complex drive 1993 Hadimioglu generated and without a nozzle circuitry et al, EUP 550,192 focussed upon the plate Complex 1993 Elrod et al, drop ejection region. fabrication EUP 572,220 Low efficiency Poor control of drop position Poor control of drop volume Thermo- An actuator which Low power Efficient aqueous IJ03, IJ09, IJ17, elastic bend relies upon differential consumption operation requires a IJ18, IJ19, IJ20, actuator thermal expansion Many ink types thermal insulator on IJ21, IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27, IJ28, used. Simple planar Corrosion IJ29, IJ30, IJ31, fabrication prevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35, IJ36, IJ37, required for each Pigmented inks IJ38, IJ39, IJ40, actuator may be infeasible, IJ41 Fast operation as pigment particles High efficiency may jam the bend CMOS actuator compatible voltages and currents Standard MEMS processes can be used Easy extension from single nozzles to pagewidth print heads High CTE A material with a very High force can be Requires special IJ09, IJ17, IJ18, thermo- high coefficient of generated material (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermal expansion Three methods of Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as PTFE deposition are deposition process, IJ28, IJ29, IJ30, polytetrafluoroethylene under development: which is not yet IJ31, IJ42, IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTE materials are deposition (CVD), fabs usually non- spin coating, and PTFE deposition conductive, a heater evaporation cannot be followed fabricated from a PTFE is a with high conductive material is candidate for low temperature (above incorporated. A 50 μm dielectric constant 350° C.) processing long PTFE bend insulation in ULSI Pigmented inks actuator with Very low power may be infeasible, polysilicon heater and consumption as pigment particles 15 mW power input Many ink types may jam the bend can provide 180 μN can be used actuator force and 10 μm Simple planar deflection. Actuator fabrication motions include: Small chip area Bend required for each Push actuator Buckle Fast operation Rotate High efficiency CMOS compatible voltages and currents Easy extension from single nozzles to pagewidth print heads Conduct-ive A polymer with a high High force can be Requires special IJ24 polymer coefficient of thermal generated materials thermo- expansion (such as Very low power development (High elastic PTFE) is doped with consumption CTE conductive actuator conducting substances Many ink types polymer) to increase its can be used Requires a PTFE conductivity to about 3 Simple planar deposition process, orders of magnitude fabrication which is not yet below that of copper. Small chip area standard in ULSI The conducting required for each fabs polymer expands when actuator PTFE deposition resistively heated. Fast operation cannot be followed Examples of High efficiency with high conducting dopants CMOS temperature (above include: compatible voltages 350° C.) processing Carbon nanotubes and currents Evaporation and Metal fibers Easy extension CVD deposition Conductive polymers from single nozzles techniques cannot such as doped to pagewidth print be used polythiophene heads Pigmented inks Carbon granules may be infeasible as pigment particles may jam the bend actuator Shape A shape memory alloy High force is Fatigue limits IJ26 memory such as TiNi (also available (stresses of maximum number alloy known as Nitinol- hundreds of MPa) of cycles Nickel Titanium alloy Large strain is Low strain (1%) developed at the Naval available (more than is required to extend Ordnance Laboratory) 3%) fatigue resistance is thermally switched High corrosion Cycle rate limited between its weak resistance by heat removal martensitic state and Simple Requires unusual its high stiffness construction materials (TiNi) austenic state. The Easy extension The latent heat of shape of the actuator from single nozzles transformation must in its martensitic state to pagewidth print be provided is deformed relative to heads High current the austenic shape. Low voltage operation The shape change operation Requires pre- causes ejection of a stressing to distort drop. the martensitic state Linear Linear magnetic Linear Magnetic Requires unusual IJ12 Magnetic actuators include the actuators can be semiconductor Actuator Linear Induction constructed with materials such as Actuator (LIA), Linear high thrust, long soft magnetic alloys Permanent Magnet travel, and high (e.g. CoNiFe) Synchronous Actuator efficiency using Some varieties (LPMSA), Linear planar also require Reluctance semiconductor permanent magnetic Synchronous Actuator fabrication materials such as (LRSA), Linear techniques Neodymium iron Switched Reluctance Long actuator boron (NdFeB) Actuator (LSRA), and travel is available Requires complex the Linear Stepper Medium force is multi-phase drive Actuator (LSA). available circuitry Low voltage High current operation operation

BASIC OPERATION MODE Description Advantages Disadvantages Examples Actuator This is the simplest ♦ Simple operation ♦ Drop repetition ♦ Thermal ink jet directly mode of operation: the ♦ No external fields rate is usually ♦ Piezoelectric ink pushes ink actuator directly required limited to around 10 jet supplies sufficient ♦ Satellite drops can kHz. However, this ♦ IJ01, IJ02, IJ03, kinetic energy to expel be avoided if drop is not fundamental IJ04, IJ05, IJ06, the drop. The drop velocity is less than to the method, but is IJ07, IJ09, IJ11, must have a sufficient 4 m/s related to the refill IJ12, IJ14, IJ16, velocity to overcome ♦ Can be efficient, method normally IJ20, IJ22, IJ23, the surface tension. depending upon the used IJ24, IJ25, IJ26, actuator used ♦ All of the drop IJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32, be provided by the IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, ♦ Satellite drops IJ39, IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44 velocity is greater than 4.5 m/s Proximity The drops to be ♦ Very simple print ♦ Requires close ♦ Silverbrook, EP printed are selected by head fabrication can proximity between 0771 658 A2 and some manner (e.g. be used the print head and related patent thermally induced ♦ The drop the print media or applications surface tension selection means transfer roller reduction of does not need to ♦ May require two pressurized ink). provide the energy print heads printing Selected drops are required to separate alternate rows of the separated from the ink the drop from the image in the nozzle by nozzle ♦ Monolithic color contact with the print print heads are medium or a transfer difficult roller. Electro- The drops to be ♦ Very simple print ♦ Requires very ♦ Silverbrook, EP static pull printed are selected by head fabrication can high electrostatic 0771 658 A2 and on ink some manner (e.g. be used field related patent thermally induced ♦ The drop ♦ Electrostatic field applications surface tension selection means for small nozzle ♦ Tone-Jet reduction of does not need to sizes is above air pressurized ink). provide the energy breakdown Selected drops are required to separate ♦ Electrostatic field separated from the ink the drop from the may attract dust in the nozzle by a nozzle strong electric field. Magnetic The drops to be ♦ Very simple print ♦ Requires magnetic ♦ Silverbrook, EP pull on ink printed are selected by head fabrication can ink 0771 658 A2 and some manner (e.g. be used ♦ Ink colors other related patent thermally induced ♦ The drop than black are applications surface tension selection means difficult reduction of does not need to ♦ Requires very pressurized ink). provide the energy high magnetic fields Selected drops are required to separate separated from the ink the drop from the in the nozzle by a nozzle strong magnetic field acting on the magnetic ink. Shutter The actuator moves a ♦ High speed (>50 ♦ Moving parts are ♦ IJ13, IJ17, IJ21 shutter to block ink kHz) operation can required flow to the nozzle. The be achieved due to ♦ Requires ink ink pressure is pulsed reduced refill time pressure modulator at a multiple of the ♦ Drop timing can ♦ Friction and wear drop ejection be very accurate must be considered frequency. ♦ The actuator ♦ Stiction is energy can be very possible low Shuttered The actuator moves a ♦ Actuators with ♦ Moving parts are ♦ IJ08, IJ15, IJ18, grill shutter to block ink small travel can be required IJ19 flow through a grill to used ♦ Requires ink the nozzle. The shutter ♦ Actuators with pressure modulator movement need only small force can be ♦ Friction and wear be equal to the width used must be considered of the grill holes. ♦ High speed (>50 ♦ Stiction is kHz) operation can possible be achieved Pulsed A pulsed magnetic ♦ Extremely low ♦ Requires an ♦ IJ10 magnetic field attracts an ‘ink energy operation is external pulsed pull on ink pusher’ at the drop possible magnetic field pusher ejection frequency. An ♦ No heat ♦ Requires special actuator controls a dissipation problems materials for both catch, which prevents the actuator and the the ink pusher from ink pusher moving when a drop is ♦ Complex not to be ejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples None The actuator directly ♦ Simplicity of ♦ Drop ejection ♦ Most ink jets, fires the ink drop, and construction energy must be including there is no external ♦ Simplicity of supplied by piezoelectric and field or other operation individual nozzle thermal bubble. mechanism required. ♦ Small physical actuator ♦ IJ01, IJ02, IJ03, size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ42, IJ42, IJ43, IJ44 Oscillating The ink pressure ♦ Oscillating ink ♦ Requires external ♦ Silverbrook, EP ink pressure oscillates, providing pressure can provide ink pressure 0771 658 A2 and (including much of the drop a refill pulse, oscillator related patent acoustic ejection energy. The allowing higher ♦ Ink pressure phase applications stimul- actuator selects which operating speed and amplitude must ♦ IJ08, IJ13, IJ15, ation) drops are to be fired ♦ The actuators may be carefully IJ17, IJ18, IJ19, by selectively blocking operate with much controlled IJ21 or enabling nozzles. lower energy ♦ Acoustic The ink pressure ♦ Acoustic lenses reflections in the ink oscillation may be can be used to focus chamber must be achieved by vibrating the sound on the designed for the print head, or nozzles preferably by an actuator in the ink supply. Media The print head is ♦ Low power ♦ Precision ♦ Silverbrook, EP proximity placed in close ♦ High accuracy assembly required 0771 658 A2 and proximity to the print ♦ Simple print head ♦ Paper fibers may related patent medium. Selected construction cause problems applications drops protrude from ♦ Cannot print on the print head further rough substrates than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer Drops are printed to a ♦ High accuracy ♦ Bulky ♦ Silverbrook, EP roller transfer roller instead ♦ Wide range of ♦ Expensive 0771 658 A2 and of straight to the print print substrates can ♦ Complex related patent medium. A transfer be used construction applications roller can also be used ♦ Ink can be dried ♦ Tektronix hot for proximity drop on the transfer roller melt piezoelectric separation. ink jet ♦ Any of the IJ series Electro- An electric field is ♦ Low power ♦ Field strength ♦ Silverbrook, EP static used to accelerate ♦ Simple print head required for 0771 658 A2 and selected drops towards construction separation of small related patent the print medium. drops is near or applications above air ♦ Tone-Jet breakdown Direct A magnetic field is ♦ Low power ♦ Requires magnetic ♦ Silverbrook, EP magnetic used to accelerate ♦ Simple print head ink 0771 658 A2 and field selected drops of construction ♦ Requires strong related patent magnetic ink towards magnetic field applications the print medium. Cross The print head is ♦ Does not require ♦ Requires external ♦ IJ06, IJ16 magnetic placed in a constant magnetic materials magnet field magnetic field. The to be integrated in ♦ Current densities Lorenz force in a the print head may be high, current carrying wire manufacturing resulting in is used to move the process electromigration actuator. problems Pulsed A pulsed magnetic ♦ Very low power ♦ Complex print ♦ IJ10 magnetic field is used to operation is possible head construction field cyclically attract a ♦ Small print head ♦ Magnetic paddle, which pushes size materials required in on the ink. A small print head actuator moves a catch, which selectively prevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples None No actuator ♦ Operational ♦ Many actuator ♦ Thermal Bubble mechanical simplicity mechanisms have Ink jet amplification is used. insufficient travel, ♦ IJ01, IJ02, IJ06, The actuator directly or insufficient force, IJ07, IJ16, IJ25, drives the drop to efficiently drive IJ26 ejection process. the drop ejection process Differential An actuator material ♦ Provides greater ♦ High stresses are ♦ Piezoelectric expansion expands more on one travel in a reduced involved ♦ IJ03, IJ09, IJ17, bend side than on the other. print head area ♦ Care must be IJ18, IJ19, IJ20, actuator The expansion may be taken that the IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24, IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, other mechanism. The ♦ Residual bend IJ33, IJ34, IJ35, bend actuator converts resulting from high IJ36, IJ37, IJ38, a high force low travel temperature or high IJ39, IJ42, IJ43, actuator mechanism to stress during IJ44 high travel, lower formation force mechanism. Transient A trilayer bend ♦ Very good ♦ High stresses are ♦ IJ40, IJ4l bend actuator where the two temperature stability involved actuator outside layers are ♦ High speed, as a ♦ Care must be identical. This cancels new drop can be taken that the bend due to ambient fired before heat materials do not temperature and dissipates delaminate residual stress. The ♦ Cancels residual actuator only responds stress of formation to transient heating of one side or the other. Reverse The actuator loads a ♦ Better coupling to ♦ Fabrication ♦ IJ05, IJ11 spring spring. When the the ink complexity actuator is turned off, ♦ High stress in the the spring releases. spring This can reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection. Actuator A series of thin ♦ Increased travel ♦ Increased ♦ Some stack actuators are stacked. ♦ Reduced drive fabrication piezoelectric ink jets This can be voltage complexity ♦ IJ04 appropriate where ♦ Increased actuators require high possibility of short electric field strength, circuits due to such as electrostatic pinholes and piezoelectric actuators. Multiple Multiple smaller ♦ Increases the ♦ Actuator forces ♦ IJ12, IJ13, IJ18, actuators actuators are used force available from may not add IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducing IJ42, IJ43 move the ink. Each ♦ Multiple actuators efficiency actuator need provide can be positioned to only a portion of the control ink flow force required. accurately Linear A linear spring is used ♦ Matches low ♦ Requires print ♦ IJ15 Spring to transform a motion travel actuator with head area for the with small travel and higher travel spring high force into a requirements longer travel, lower ♦ Non-contact force motion. method of motion transformation Coiled A bend actuator is ♦ Increases travel ♦ Generally ♦ IJ17, IJ21, IJ34, actuator coiled to provide ♦ Reduces chip area restricted to planar IJ35 greater travel in a ♦ Planar implementations due reduced chip area. implementations are to extreme relatively easy to fabrication difficulty fabricate. in other orientations. Flexure A bend actuator has a ♦ Simple means of ♦ Care must be ♦ IJ10, IJ19, IJ33 bend small region near the increasing travel of taken not to exceed actuator fixture point, which a bend actuator the elastic limit in flexes much more the flexure area readily than the ♦ Stress distribution remainder of the is very uneven actuator. The actuator ♦ Difficult to flexing is effectively accurately model converted from an with finite element even coiling to an analysis angular bend, resulting in greater travel of the actuator tip. Catch The actuator controls a ♦ Very low actuator ♦ Complex ♦ IJ10 small catch. The catch energy construction either enables or ♦ Very small ♦ Requires external disables movement of actuator size force an ink pusher that is ♦ Unsuitable for controlled in a bulk pigmented inks manner. Gears Gears can be used to ♦ Low force, low ♦ Moving parts are ♦ IJ13 increase travel at the travel actuators can required expense of duration. be used ♦ Several actuator Circular gears, rack ♦ Can be fabricated cycles are required and pinion, ratchets, using standard ♦ More complex and other gearing surface MEMS drive electronics methods can be used. processes ♦ Complex construction ♦ Friction, friction, and wear are possible Buckle plate A buckle plate can be ♦ Very fast ♦ Must stay within ♦ S. Hirata et al, used to change a slow movement elastic limits of the “An Ink-jet Head actuator into a fast achievable materials for long Using Diaphragm motion. It can also device life Microactuator”, convert a high force, ♦ High stresses Proc. IEEE MEMS low travel actuator into involved Feb. 1996, pp 418- a high travel, medium ♦ Generally high 423. force motion. power requirement ♦ IJ18, IJ27 Tapered A tapered magnetic ♦ Linearizes the ♦ Complex ♦ IJ14 magnetic pole can increase magnetic construction pole travel at the expense of force/distance curve force. Lever A lever and fulcrum is ♦ Matches low ♦ High stress ♦ IJ32, IJ36, IJ37 used to transform a travel actuator with around the fulcrum motion with small higher travel travel and high force requirements into a motion with ♦ Fulcrum area has longer travel and lower no linear movement, force. The lever can and can be used for also reverse the a fluid seal direction of travel. Rotary The actuator is ♦ High mechanical ♦ Complex ♦ IJ28 impeller connected to a rotary advantage construction impeller. A small ♦ The ratio of force ♦ Unsuitable for angular deflection of to travel of the pigmented inks the actuator results in a actuator can be rotation of the impeller matched to the vanes, which push the nozzle requirements ink against stationary by varying the vanes and out of the number of impeller nozzle. vanes Acoustic A refractive or ♦ No moving parts ♦ Large area ♦ 1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192 plate) acoustic lens is ♦ Only relevant for ♦ 1993 Elrod et al, used to concentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharp point is used ♦ Simple ♦ Difficult to ♦ Tone-jet conductive to concentrate an construction fabricate using point electrostatic field. standard VLSI processes for a surface ejecting ink- jet ♦ Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume The volume of the ♦ Simple ♦ High energy is ♦ Hewlett-Packard expansion actuator changes, construction in the typically required to Thermal Ink jet pushing the ink in all case of thermal ink achieve volume ♦ Canon Bubblejet directions. jet expansion. This leads to thermal stress, cavitation, and kogation in thermal ink jet implementations Linear, The actuator moves in ♦ Efficient coupling ♦ High fabrication ♦ IJ01, IJ02, IJ04, normal to a direction normal to to ink drops ejected complexity may be IJ07, IJ11, IJ14 chip surface the print head surface. normal to the required to achieve The nozzle is typically surface perpendicular in the line of motion movement. Parallel to The actuator moves ♦ Suitable for ♦ Fabrication ♦ IJ12, IJ13, IJ15, chip surface parallel to the print planar fabrication complexity IJ33, , IJ34, IJ35, head surface. Drop ♦ Friction IJ36 ejection may still be ♦ Stiction normal to the surface. Membrane An actuator with a ♦ The effective area ♦ Fabrication ♦ 1982 Howkins push high force but small of the actuator complexity U.S. Pat. No. 4,459,601 area is used to push a becomes the ♦ Actuator size stiff membrane that is membrane area ♦ Difficulty of in contact with the ink. integration in a VLSI process Rotary The actuator causes ♦ Rotary levers may ♦ Device ♦ IJ05, IJ08, IJ13, the rotation of some be used to increase complexity IJ28 element, such a grill or travel ♦ May have friction impeller ♦ Small chip area at a pivot point requirements Bend The actuator bends ♦ A very small ♦ Requires the ♦ 1970 Kyser et al when energized. This change in actuator to be made U.S. Pat. No. 3,946,398 may be due to dimensions can be from at least two ♦ 1973 Stemme differential thermal converted to a large distinct layers, or to U.S. Pat. No. 3,747,120 expansion, motion. have a thermal ♦ IJ03, IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24, expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33, IJ34, other form of relative IJ35 dimensional change. Swivel The actuator swivels ♦ Allows operation ♦ Inefficient ♦ IJ06 around a central pivot. where the net linear coupling to the ink This motion is suitable force on the paddle motion where there are is zero opposite forces ♦ Small chip area applied to opposite requirements sides of the paddle, e.g. Lorenz force. Straighten The actuator is ♦ Can be used with ♦ Requires careful ♦ IJ26, IJ32 normally bent, and shape memory balance of stresses straightens when alloys where the to ensure that the energized. austenic phase is quiescent bend is planar accurate Double The actuator bends in ♦ One actuator can ♦ Difficult to make ♦ IJ36, IJ37, IJ38 bend one direction when be used to power the drops ejected by one element is two nozzles. both bend directions energized, and bends ♦ Reduced chip identical. the other way when size. ♦ A small efficiency another element is ♦ Not sensitive to loss compared to energized. ambient temperature equivalent single bend actuators. Shear Energizing the ♦ Can increase the ♦ Not readily ♦ 1985 Fishbeck actuator causes a shear effective travel of applicable to other U.S. Pat. No. 4,584,590 motion in the actuator piezoelectric actuator material. actuators mechanisms Radial con- The actuator squeezes ♦ Relatively easy to ♦ High force ♦ 1970 Zoltan U.S. Pat. No. striction an ink reservoir, fabricate single required 3,683,212 forcing ink from a nozzles from glass ♦ Inefficient constricted nozzle. tubing as ♦ Difficult to macroscopic integrate with VLSI structures processes Coil/uncoil A coiled actuator ♦ Easy to fabricate ♦ Difficult to ♦ IJ17, IJ2l, IJ34, uncoils or coils more as a planar VLSl fabricate for non- IJ35 tightly. The motion of process planar devices the free end of the ♦ Small area ♦ Poor out-of-plane actuator ejects the ink. required, therefore stiffness low cost Bow The actuator bows (or ♦ Can increase the ♦ Maximum travel ♦ IJ16, IJ18, IJ27 buckles) in the middle speed of travel is constrained when energized. ♦ Mechanically ♦ High force rigid required Push-Pull Two actuators control ♦ The structure is ♦ Not readily ♦ IJ18 a shutter. One actuator pinned at both ends, suitable for ink jets pulls the shutter, and so has a high out-of- which directly push the other pushes it. plane rigidity the ink Curl A set of actuators curl ♦ Good fluid flow ♦ Design ♦ IJ20, IJ42 inwards inwards to reduce the to the region behind complexity volume of ink that the actuator they enclose. increases efficiency Curl A set of actuators curl ♦ Relatively simple ♦ Relatively large ♦ IJ43 outwards outwards, pressurizing construction chip area ink in a chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes enclose ♦ High efficiency ♦ High fabrication ♦ IJ22 a volume of ink. These ♦ Small chip area complexity simultaneously rotate, ♦ Not suitable for reducing the volume pigmented inks between the vanes. Acoustic The actuator vibrates ♦ The actuator can ♦ Large area ♦ 1993 Hadimioglu vibration at a high frequency. be physically distant required for efficient et al, EUP 550,192 from the ink operation at useful ♦ 1993 Elrod et al, frequencies EUP 572,220 ♦ Acoustic coupling and crosstalk ♦ Complex drive circuitry ♦ Poor control of drop volume and position None In various ink jet ♦ No moving parts ♦ Various other ♦ Silverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and does not move. required to eliminate related patent moving parts applications ♦ Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages Examples Surface This is the normal way ♦ Fabrication ♦ Low speed ♦ Thermal ink jet tension that ink jets are simplicity ♦ Surface tension ♦ Piezoelectric ink refilled. After the ♦ Operational force relatively jet actuator is energized, simplicity small compared to ♦ IJ01-IJ07, IJ10- it typically returns actuator force IJ14, IJ16, IJ20, rapidly to its normal ♦ Long refill time IJ22-IJ45 position. This rapid usually dominates return sucks in air the total repetition through the nozzle rate opening. The ink surface tension at the nozzle then exerts a small force restoring the meniscus to a minimum area. This force refills the nozzle. Shuttered Ink to the nozzle ♦ High speed ♦ Requires common ♦ IJ08, IJ13, IJ15, oscillating chamber is provided at ♦ Low actuator ink pressure IJ17, IJ18, IJ19, ink pressure a pressure that energy, as the oscillator IJ21 oscillates at twice the actuator need only ♦ May not be drop ejection open or close the suitable for frequency. When a shutter, instead of pigmented inks drop is to be ejected, ejecting the ink drop the shutter is opened for 3 half cycles: drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill After the main actuator ♦ High speed, as the ♦ Requires two ♦ IJ09 actuator has ejected a drop a nozzle is actively independent second (refill) actuator refilled actuators per nozzle is energized. The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive ink The ink is held a slight ♦ High refill rate, ♦ Surface spill must ♦ Silverbrook, EP pressure positive pressure. therefore a high be prevented 0771 658 A2 and After the ink drop is drop repetition rate ♦ Highly related patent ejected, the nozzle is possible hydrophobic print applications chamber fills quickly head surfaces are ♦ Alternative for:, as surface tension and required IJ01-IJ07, IJ10- ink pressure both IJ14, IJ16, IJ20, operate to refill the IJ22-IJ45 nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Long inlet The ink inlet channel ♦ Design simplicity ♦ Restricts refill rate ♦ Thermal ink jet channel to the nozzle chamber ♦ Operational ♦ May result in a ♦ Piezoelectric ink is made long and simplicity relatively large chip jet relatively narrow, ♦ Reduces crosstalk area ♦ IJ42, IJ43 relying on viscous ♦ Only partially drag to reduce inlet effective back-flow. Positive ink The ink is under a ♦ Drop selection ♦ Requires a ♦ Silverbrook, EP pressure positive pressure, so and separation method (such as a 0771 658 A2 and that in the quiescent forces can be nozzle rim or related patent state some of the ink reduced effective applications drop already protrudes ♦ Fast refill time hydrophobizing, or ♦ Possible operation from the nozzle. both) to prevent of the following: This reduces the flooding of the IJ01-IJ07, IJ09- pressure in the nozzle ejection surface of IJ12, IJ14, IJ16, chamber which is the print head. IJ20, IJ22, , IJ23- required to eject a IJ34, IJ36-IJ41, certain volume of ink. IJ44 The reduction in chamber pressure results in a reduction in ink pushed out through the inlet. Baffle One or more baffles ♦ The refill rate is ♦ Design ♦ HP Thermal Ink are placed in the inlet not as restricted as complexity Jet ink flow. When the the long inlet ♦ May increase ♦ Tektronix actuator is energized, method. fabrication piezoelectric ink jet the rapid ink ♦ Reduces crosstalk complexity (e.g. movement creates Tektronix hot melt eddies which restrict Piezoelectric print the flow through the heads). inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible flap In this method recently ♦ Significantly ♦ Not applicable to ♦ Canon restricts disclosed by Canon, reduces back-flow most ink jet inlet the expanding actuator for edge-shooter configurations (bubble) pushes on a thermal ink jet ♦ Increased flexible flap that devices fabrication restricts the inlet. complexity ♦ Inelastic deformation of polymer flap results in creep over extended use Inlet filter A filter is located ♦ Additional ♦ Restricts refill rate ♦ IJ04, IJ12, IJ24, between the ink inlet advantage of ink ♦ May result in IJ27, IJ29, IJ30 and the nozzle filtration complex chamber. The filter has ♦ Ink filter may be construction a multitude of small fabricated with no holes or slots, additional process restricting ink flow. steps The filter also removes particles which may block the nozzle. Small inlet The ink inlet channel ♦ Design simplicity ♦ Restricts refill rate ♦ IJ02, IJ37, IJ44 compared to the nozzle chamber ♦ May result in a to nozzle has a substantially relatively large chip smaller cross section area than that of the nozzle ♦ Only partially resulting in easier ink effective egress out of the nozzle than out of the inlet. Inlet shutter A secondary actuator ♦ Increases speed of ♦ Requires separate ♦ IJ09 controls the position of the ink-jet print refill actuator and a shutter, closing off head operation drive circuit the ink inlet when the main actuator is energized. The inlet is The method avoids the ♦ Back-flow ♦ Requires careful ♦ IJ01, IJ03, IJ05, located problem of inlet back- problem is design to minimize IJ06, IJ07, IJ10, behind the flow by arranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushing ink-pushing surface of pressure behind the IJ22, 1123, IJ25, surface the actuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34, IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and a ♦ Significant ♦ Small increase in ♦ IJ07, IJ20, IJ26, actuator wall of the ink reductions in back- fabrication IJ38 moves to chamber are arranged flow can be complexity shut off the so that the motion of achieved inlet the actuator closes off ♦ Compact designs the inlet. possible Nozzle In some configurations ♦ Ink back-flow ♦ None related to ♦ Silverbrook, EP actuator of ink jet, there is no problem is ink back-flow on 0771 658 A2 and does not expansion or eliminated actuation related patent result in ink movement of an applications back-flow actuator which may ♦ Valve-jet cause ink back-flow ♦ Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Normal All of the nozzles are ♦ No added ♦ May not be ♦ Most ink jet nozzle firing fired periodically, complexity on the sufficient to displace systems before the ink has a print head dried ink ♦ IJ01, IJ02, IJ03, chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09, IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20, IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26, IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, after IJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to a cleaning IJ39, IJ40,, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra In systems which heat ♦ Can be highly ♦ Requires higher ♦ Silverbrook, EP power to the ink, but do not boil effective if the drive voltage for 0771 658 A2 and ink heater it under normal heater is adjacent to clearing related patent situations, nozzle the nozzle ♦ May require applications clearing can be larger drive achieved by over- transistors powering the heater and boiling ink at the nozzle. Rapid The actuator is fired in ♦ Does not require ♦ Effectiveness ♦ May be used with: succession rapid succession. In extra drive circuits depends IJ01, IJ02, IJ03, of actuator some configurations, on the print head substantially upon IJ04, IJ05, IJ06, pulses this may cause heat ♦ Can be readily the configuration of IJ07, IJ09, IJ10, build-up at the nozzle controlled and the ink jet nozzle IJ11, IJ14, IJ16, which boils the ink, initiated by digital IJ20, IJ22, IJ23, clearing the nozzle. In logic IJ24, IJ25, IJ27, other situations, it may IJ28, IJ29, IJ30, cause sufficient IJ31, IJ32, IJ33, vibrations to dislodge IJ34, IJ36, IJ37, clogged nozzles. IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is ♦ A simple solution ♦ Not suitable ♦ May be used with: power to not normally driven to where applicable where there is a hard IJ03, IJ09, IJ16, ink pushing the limit of its motion, limit to actuator IJ20, IJ23, IJ24, actuator nozzle clearing may be movement IJ25, IJ27, IJ29, assisted by providing IJ30, IJ31, IJ32, an enhanced drive IJ39, IJ40, IJ41, signal to the actuator. IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is ♦ A high nozzle ♦ High ♦ IJ08, IJ13, IJ15, resonance applied to the ink clearing capability implementation cost IJ17, IJ18, IJ19 chamber. This wave is can be achieved if system does not IJ21 of an appropriate ♦ May be already include an amplitude and implemented at very acoustic actuator frequency to cause low cost in systems sufficient force at the which already nozzle to clear include acoustic blockages. This is actuators easiest to achieve if the ultransonic wave is at a resonant frequency of the ink cavity. Nozzle A microfabricated ♦ Can clear severely ♦ Accurate ♦ Silverbrook, EP clearing plate is pushed against clogged nozzles mechanical 0771 658 A2 and plate the nozzles. The plate alignment is related patent has a post for every required applications nozzle. A post moves ♦ Moving parts are through each nozzle, required displacing dried ink. ♦ There is risk of damage to the nozzles ♦ Accurate fabrication is required Ink The pressure of the ink ♦ May be effective ♦ Requires pressure ♦ May be used with pressure is temporarily where other pump or other all IJ series ink jets pulse increased so that ink methods cannot be pressure actuator streams from all of the used ♦ Expensive nozzles. This may be ♦ Wasteful of ink used in conjunction with actuator energizing. Print head A flexible ‘blade’ is ♦ Effective for ♦ Difficult to use if ♦ Many ink jet wiper wiped across the print planar print head print head surface is systems head surface. The surfaces non-planar or very blade is usually ♦ Low cost fragile fabricated from a ♦ Requires flexible polymer, e.g. mechanical parts rubber or synthetic ♦ Blade can wear elastomer. out in high volume print systems Separate A separate heater is ♦ Can be effective ♦ Fabrication ♦ Can be used with ink boiling provided at the nozzle where other nozzle complexity many IJ series ink heater although the normal clearing methods jets drop e-ection cannot be used mechanism does not ♦ Can be require it. The heaters implemented at no do not require additional cost in individual drive some ink jet circuits, as many configurations nozzles can be cleared simultaneously, and no imaging is required.

Description Advantages Disadvantages Examples NOZZLE PLATE CONSTRUCTION Electro- A nozzle plate is ♦ Fabrication ♦ High temperatures ♦ Hewlett Packard formed separately fabricated simplicity and pressures are Thermal Ink jet nickel from electroformed required to bond nickel, and bonded to nozzle plate the print head chip. ♦ Minimum thickness constraints ♦ Differential thermal expansion Laser Individual nozzle ♦ No masks ♦ Each hole must be ♦ Canon Bubblejet ablated or holes are ablated by an required individually formed ♦ 1988 Sercet et al., drilled intense UV laser in a ♦ Can be quite fast ♦ Special equipment SPIE, Vol. 998 polymer nozzle plate, which is ♦ Some control over required Excimer Beam typically a polymer nozzle profile is ♦ Slow where there Applications, pp. such as polyimide or possible are many thousands 76-83 polysulphone ♦ Equipment of nozzles per print ♦ 1993 Watanabe et required is relatively head al., U.S. Pat. No. 5,208,604 low cost ♦ May produce thin burrs at exit holes Silicon A separate nozzle ♦ High accuracy is ♦ Two part ♦ K. Bean, IEEE micro- plate is micromachined attainable construction Transactions on machined from single crystal ♦ High cost Electron Devices, silicon, and bonded to ♦ Requires Vol. ED-25, No. 10, the print head wafer. precision alignment 1978, pp 1185-1195 ♦ Nozzles may be ♦ Xerox 1990 clogged by adhesive Hawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries ♦ No expensive ♦ Very small nozzle ♦ 1970 Zoltan U.S. Pat. No. capillaries are drawn from glass equipment required sizes are difficult to 3,683,212 tubing. This method ♦ Simple to make form has been used for single nozzles ♦ Not suited for making individual mass production nozzles, but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is ♦ High accuracy (<1 ♦ Requires ♦ Silverbrook, EP surface deposited as a layer μm) sacrificial layer 0771 658 A2 and micro- using standard VLSI ♦ Monolithic under the nozzle related patent machined deposition techniques. ♦ Low cost plate to form the applications using VLSI Nozzles are etched in ♦ Existing processes nozzle chamber ♦ IJ01, IJ02, IJ04, litho- the nozzle plate using can be used ♦ Surface may be IJ11, IJ12, IJ17, graphic VLSI lithography and fragile to the touch IJ18, IJ20, IJ22, processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a ♦ High accuracy (<1 ♦ Requires long ♦ IJ03, IJ05, IJ06, etched buried etch stop in the μm) etch times IJ07, IJ08, IJ09, through wafer. Nozzle ♦ Monolithic ♦ Requires a IJ10, IJ13, IJ14, substrate chambers are etched in ♦ Low cost support wafer IJ15, IJ16, IJ19, the front of the wafer, ♦ No differential IJ21, IJ23, IJ25, and the wafer is expansion IJ26 thinned from the back side. Nozzles are then etched in the etch stop layer. No nozzle Various methods have ♦ No nozzles to ♦ Difficult to ♦ Ricoh 1995 plate been tried to eliminate become clogged control drop Sekiya et al U.S. Pat. No. the nozzles entirely, to position accurately 5,412,413 prevent nozzle ♦ Crosstalk ♦ 1993 Hadimioglu clogging. These problems et al EUP 550,192 include thermal bubble ♦ 1993 Elrod et al mechanisms and EUP 572,220 acoustic lens mechanisms Trough Each drop ejector has ♦ Reduced ♦ Drop firing ♦ IJ35 a trough through which manufacturing direction is sensitive a paddle moves. There complexity to wicking. is no nozzle plate. ♦ Monolithic Nozzle slit The elimination of ♦ No nozzles to ♦ Difficult to ♦ 1989 Saito et al instead of nozzle holes and become clogged control drop U.S. Pat. No. 4,799,068 individual replacement by a slit position accurately nozzles encompassing many ♦ Crosstalk actuator positions problems reduces nozzle clogging, but increases crosstalk due to ink surface waves DROP EJECTION DIRECTION Edge Ink flow is along the ♦ Simple ♦ Nozzles limited to ♦ Canon Bubblejet (‘edge surface of the chip, construction edge 1979 Endo et al GB shooter’) and ink drops are ♦ No silicon etching ♦ High resolution is patent 2,007,162 ejected from the chip required difficult ♦ Xerox heater-in- edge. ♦ Good heat sinking ♦ Fast color printing pit 1990 Hawkins et via substrate requires one print al U.S. Pat. No. 4,899,181 ♦ Mechanically head per color ♦ Tone-jet strong ♦ Ease of chip handing

DROP EJECTION DIRECTION Description Advantages Disadvantages Examples Surface Ink flow is along the ♦ No bulk silicon ♦ Maximum ink ♦ Hewlett-Packard (‘roof surface of the chip, etching required flow is severely TIJ 1982 Vaught et shooter’) and ink drops are ♦ Silicon can make restricted al U.S. Pat. No. 4,490,728 ejected from the chip an effective heat ♦ IJ02, IJ11, IJ12, surface, normal to the sink IJ20, IJ22 plane of the chip. ♦ Mechanical strength Through Ink flow is through the ♦ High ink flow ♦ Requires bulk ♦ Silverbrook, EP chip, chip, and ink drops are ♦ Suitable for silicon etching 0771 658 A2 and forward ejected from the front pagewidth print related patent (‘up surface of the chip. heads applications shooter’) ♦ High nozzle ♦ IJ04, IJ17, IJ18, packing density IJ24, IJ27-IJ45 therefore low manufacturing cost Through Ink flow is through the ♦ High ink flow ♦ Requires wafer ♦ IJ01, IJ03, IJ05, chip, chip, and ink drops are ♦ Suitable for thinning IJ06, IJ07, IJ08, reverse ejected from the rear pagewidth print ♦ Requires special IJ09, IJ10, IJ13, (‘down surface of the chip. heads handling during IJ14, IJ15, IJ16, shooter’) ♦ High nozzle manufacture IJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore low manufacturing cost Through Ink flow is through the ♦ Suitable for ♦ Pagewidth print ♦ Epson Stylus actuator actuator, which is not piezoelectric print heads require ♦ Tektronix hot fabricated as part of heads several thousand melt piezoelectric the same substrate as connections to drive ink jets the drive transistors. circuits ♦ Cannot be manufactured in standard CMOS fabs ♦ Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Water based ink which ♦ Environmentally ♦ Slow drying ♦ Most existing ink dye typically contains: friendly ♦ Corrosive jets water, dye, surfactant, ♦ No odor ♦ Bleeds on paper ♦ All IJ series ink humectant, and ♦ May strikethrough jets biocide. ♦ Cockles paper ♦ Silverbrook, EP Modern ink dyes have 0771 658 A2 and high water-fastness, related patent light fastness applications Aqueous, Water based ink which ♦ Environmentally ♦ Slow drying ♦ IJ02, IJ04, IJ21, pigment typically contains: friendly ♦ Corrosive IJ26, IJ27, IJ30 water, pigment, ♦ No odor ♦ Pigment may clog ♦ Silverbrook, EP surfactant, humectant, ♦ Reduced bleed nozzles 0771 658 A2 and and biocide. ♦ Reduced wicking ♦ Pigment may clog related patent Pigments have an ♦ Reduced actuator applications advantage in reduced strikethrough mechanisms ♦ Piezoelectric ink- bleed, wicking and ♦ Cockles paper jets strikethrough. ♦ Thermal ink jets (with significant restrictions) Methyl MEK is a highly ♦ Very fast drying ♦ Odorous ♦ All IJ series ink Ethyl volatile solvent used ♦ Prints on various ♦ Flammable jets Ketone for industrial printing substrates such as (MEK) on difficult surfaces metals and plastics such as aluminum cans. Alcohol Alcohol based inks can ♦ Fast drying ♦ Slight odor ♦ All IJ series ink (ethanol, 2- be used where the ♦ Operates at sub- ♦ Flammable jets butanol, printer must operate at freezing and others) temperatures below the temperatures freezing point of ♦ Reduced paper water. An example of cockle this is in-camera ♦ Low cost consumer photographic printing. Phase The ink is solid at ♦ No drying time- ♦ High viscosity ♦ Tektronix hot change room temperature, and ink instantly freezes ♦ Printed ink melt piezoelectric (hot melt) is melted in the print on the print medium typically has a ink jets head before jetting. ♦ Almost any print ‘waxy’ feel ♦ 1989 Nowak U.S. Pat. No. Hot melt inks are medium can be used ♦ Printed pages may 4,820,346 usually wax based, ♦ No paper cockle ‘block’ ♦ All IJ series ink with a melting point occurs ♦ Ink temperature jets around 80° C. After ♦ No wicking may be above the jetting the ink freezes occurs curie point of almost instantly upon ♦ No bleed occurs permanent magnets contacting the print ♦ No strikethrough ♦ Ink heaters medium or a transfer occurs consume power roller. ♦ Long warm-up time Oil Oil based inks are ♦ High solubility ♦ High viscosity: ♦ All IJ series ink extensively used in medium for some this is a significant jets offset printing. They dyes limitation for use in have advantages in ♦ Does not cockle ink jets, which improved paper usually require a characteristics on ♦ Does not wick low viscosity. Some paper (especially no through paper short chain and wicking or cockle). Oil multi-branched oils soluble dies and have a sufficiently pigments are required. low viscosity. ♦ Slow drying Micro- A microemulsion is a ♦ Stops ink bleed ♦ Viscosity higher ♦ All IJ series ink emulsion stable, self forming ♦ High dye than water jets emulsion of oil, water, solubility ♦ Cost is slightly and surfactant. The ♦ Water, oil, and higher than water characteristic drop size amphiphilic soluble based ink is less than 100 nm, dies can be used ♦ High surfactant and is determined by ♦ Can stabilize concentration the preferred curvature pigment suspensions required (around of the surfactant. 5%) 

We claim:
 1. A print head comprising: a nozzle chamber having at least two fluid ejection apertures defined in a wall, or walls of said chamber; a moveable paddle vane located in a plane adjacent a rim of a first one of said fluid ejection apertures; and an actuator mechanism attached to said moveable paddle vane and adapted to move said paddle vane in a first direction so as to cause the ejection of fluid drops out of said first fluid ejection aperture and to further move said paddle vane in a second alternative direction so as to cause the ejection of fluid drops out of a second one of said fluid ejection apertures.
 2. The print head as claimed in claim 1 further comprising: a baffle located between said first and second fluid ejection apertures and wherein said paddle vane moving in said first direction causes an increase in pressure of said fluid in the volume adjacent said first aperture and a simultaneous decrease in pressure of said fluid in the volume adjacent said second aperture.
 3. The print head as claimed in claim 2 wherein said paddle vane moving in said second direction causes an increase in pressure of said fluid in the volume adjacent said second aperture and a simultaneous decrease in pressure of said fluid in the volume adjacent said first aperture.
 4. The print head as claimed in claim 2 wherein said paddle vane and said actuator are joined at a fulcrum pivot point, said fulcrum pivot point comprising a thinned portion of said nozzle chamber wall.
 5. The print head as claimed in claim 4 wherein said thinned portion of said nozzle chamber wall includes a series of slots at opposing sides so as to allow for the flexing of said wall during actuation of said actuator.
 6. The print head as claimed in claim 5 wherein said slots connect internal portions of the nozzle chamber with an external ambient atmosphere and an external surface adjacent said slots comprise a planar or concave surface so as to reduce wicking.
 7. The print head as claimed in claim 1 wherein said paddle vane and said actuator are interconnected so as to pivot around a wall of said chamber and said print head further comprises: a fluid supply channel connecting said nozzle chamber with a fluid supply for supplying fluid to said nozzle chamber, said connection being in a wall of said chamber substantially adjacent the pivot point of said paddle vane.
 8. The print head as claimed in claim 1 wherein at least one wall of said nozzle chamber includes at least one smaller aperture interconnecting said nozzle chamber with an ambient atmosphere a size of said smaller aperture being of such dimensions that, during normal operation of said print head a net flow of fluid through said smaller aperture is zero.
 9. The print head as claimed in claim 1 wherein said actuator comprises a thermal actuator having at least two heater elements with a first of said elements being actuated to cause said paddle vane to move in said first direction and a second heater element being actuated to caused said paddle vane to move in said second direction.
 10. The print head as claimed in claim 9 wherein said heater elements have a high bend efficiency wherein said bend efficiency is defines as a Young's modulus of said heater elements times the coefficient of thermal expansion of said heater elements divided by a density of said heater elements and by a specific heat capacity of said heater elements.
 11. The print head as claimed in claim 9 wherein said heater elements are arranged on opposite sides of a central arm, said central arm having a low thermal conductivity.
 12. The print head as claimed in claim 11 wherein said central arm comprises substantially glass.
 13. The print head as claimed in claim 9 wherein said thermal actuator operates in an ambient atmosphere.
 14. The print head as claimed in claim 1 wherein said thermal actuator includes one end attached to a substrate and a second end having a thinned portion said thinned portion providing for the flexible attachment of said actuator to said moveable paddle vane.
 15. A multiplicity of print heads as claimed in claim 1 wherein said fluid ejection apertures are grouped together spatially into spaced apart rows and fluid is ejected from the fluid ejection apertures of each of said rows in phases.
 16. A multiplicity of print heads as claimed in claim 1 wherein said print heads are incorporated in an ink jet printer.
 17. A multiplicity of print heads as claimed in claim 16 wherein said nozzle chambers are further grouped into multiple ink colors and with each of said nozzles being supplied with a corresponding ink color.
 18. The print head as claimed in claim 1 wherein said rim of each ejection aperture is defined around an outer surface thereof.
 19. A method of ejecting drops of fluid from a nozzle chamber having at least two nozzle apertures defined in a wall, or walls of said nozzle chamber using a moveable paddle attached to an actuator mechanism, said method comprising the steps of: actuating said actuator to cause said moveable paddle to move in a first direction so as to eject drops from a first of said nozzle apertures; and actuating said actuator to cause said moveable paddle to move in a second direction so as to eject drops from a second of said nozzle apertures.
 20. A method as claimed in claim 19 wherein an array of nozzle chambers is arranged in a pagewidth print head and the moveable paddles of each nozzle chamber are driven in phase. 